While N-heterocyclic carbenes (NHCs) have been well-studied ligands for transition metal complexes, their group 14 analogues, which instead incorporate a phosphorus atom in the heterocycle, remain relatively unexplored in comparison. In contrast to NHCs, N-heterocyclic phosphenium cations (NHP+s) are weak σ-donors and strong π-acceptors, leading to different reactivity, properties, and potential applications. Similar to nitrosyl ligands, NHPs are thought to interconvert between a phosphenium (NHP+) and a phosphido (NHP-) through a two-electron process, which may offer a new avenue to unique properties and coordination. Incorporation of an NHP unit into the center of a rigid chelating pincer ligand and coordination to a nickel center has yielded a (PPClP)Ni(PMe3) complex, which can further be treated with a reagent acting as a hydride source to afford a new dimeric nickel complex [(PPHP)NiPMe3]2 in which the chloride bound to the central phosphorus is abstracted and a new P-H bond is installed. Structural characterization of this compound reveals an unprecedented structural motif in NHP coordination as the dimerization occurs through a P2N2 core of the two ligands, resulting in a bridging mode that does not involve the two transition metal centers or the hydride fragment. Furthermore, an unusual μ2-H ligand bridging between the nickel center and the central phosphorus of the NHP unit is also observed in this structure. Progress toward probing the electronic nature of the P-H bond and exploration of the novel coordination of the NHP framework will be discussed.

Exploration of novel binding modes in pincer-ligated N-heterocyclic phosphenium/phosphido nickel complexes

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.